Various types of pipes are provided inside structures such as nuclear power plants and industrial plants, which are too narrow for a worker to pass through. In order to investigate the insides of such structures, an investigation apparatus which can be remotely operated by a worker using a controller has been adopted. The investigation apparatus is connected to an externally installed controller through a cable, and performs necessary investigation in accordance with a control command received from the controller via the cable. Then, in order to allow the investigation apparatus to move efficiently inside the structure, for example, an investigation vehicle disclosed in PTL 1 has been proposed.
PTL 1 discloses the investigation vehicle in which a camera and a control substrate are mounted on an upper portion of a rectangular main body in a longitudinal direction and two sets of circular section crawlers that can rotate in two directions are attached to a lower portion of the main body.